Drop off and Run low

Drop off verb - To grow less in scope or intensity especially gradually.

Run low and drop off are semantically related In some cases you can use "Run low" instead a verb "Drop off".

Run low verb - To be spent or finished.

Drop off and run low are semantically related in decrease topic. Sometimes you can use "Drop off" instead a verb phrase "Run low", if it concerns topics such as grow less or make less.